1. Technical Field of the Invention
The invention relates to electronic musical instruments and more particularly to multi-voice electronic musical instruments employing chord transformation, i.e. instruments, which do not perform chords directly, but transform them to chords close in sound, but with different musical characteristics.
2. Description of the Prior Art
Various prior art methods of transforming close harmony chords, playable with one hand on a piano keyboard, to open harmony guitar like chords with a larger number of notes are known to be employed in keyboard based musical instruments, making it possible to emulate plucked string instruments. One of the most popular methods of chord transforming is explained in description of the electronic musical instruments (see description in U.S. Pat. No. 4,379,420, Adaptive strum keying for a keyboard electronic musical instruments). This method comprises analyzing a chord played on a keyboard, identifying its type and root note, then choosing the output chord from a previously created chord table, which matches the chord type and root note. This method does not consider melodic position of the input chord, i.e. its inversion and octave position on the keyboard, which simplifies the procedure of playing chords for the performer, but at the same time creates many significant problems as the performer does not have a possibility of controlling some very important musical characteristics of the output chords, such as their melodic position, inversion and octave position. Another prior art method of chord transforming, technically quite close to the method of the present invention (see description in U.S. Pat. No. 3,967,520, Guitar chording device for keyboard instruments) comprises using all notes of the input chord for transformation and getting the output chord of the notes, playable as a guitar chord. Every note is chosen from 5 pre-assigned notes of the 5 guitar strings using a special priority system. However this known method also has some considerable problems. It does not consider the input chord""s melodic and octave position, which makes controlling output chord""s melodic and octave position impossible. Furthermore, the range of the upper notes of the output chord is limited to 5 of 12 available semitones even in 1 octave range, plus the method does not allow all types of output chords to employ root note in one of the bass strings, which definitely destroys the chord""s harmonic color. The closest in technical aspects prototype to the method of the present invention is the method of chord transforming explained in U.S. Pat. No. 5,136,914, Stringed instruments emulator and method. This prior art method comprises the following scheme of transforming close harmony piano type chord to open harmony guitar like chord: the first received note of the input chord becomes the lowest or the highest note of the output chord, depending on whether the lowest or the highest string has been assigned as a controlling string for the chord. The rest of the notes are either left where they are, or transposed to another octave according to previously set parameters, such as open strings tuning, the number of used frets, pre-selected mode (open tuning or barred tuning). However since the input chord""s octave position is not considered, the pitch of the resulting chord""s highest note cannot be controlled by the performer. Furthermore, the prototype method does not guarantee the presence of root note in the lowest voices of the output chord. But the biggest problem of this method, along with all prior art methods, is their lack of controllability of voices leading in a chord progression, as well as impossibility of playing chords in required inversions, which is quite easy to achieve while playing on a real guitar by simply moving left hand along the neck. Also employing the above mentioned methods it is practically impossible to use more complex chord types with non-chordal or altered tones as they require controllability of voices leading, otherwise whole chord progression, even if every individual chord sounds harmonically accurate, may lose its musical sense.
The chord transforming method of the present invention includes receiving a close harmony input chord as a list of not less than 3 notes, generating open harmony resulting chord as a note list equal to or greater than the number of input notes, of the notes of the input chord included without changes and/or transposed to another octave, as well as outputting the resulting chord, comprises identifying the highest note of the input chord, which is then included in the resulting chord without changes and transposing every note of the subset of the notes to be transposed in such a way, that every transposed note is lower in pitch, than the highest note of the input chord. Furthermore, one of the preferred cases of the method of the present invention also comprises identifying root note of the input chord and transposing every note of selected subset of the notes to be transposed to another octave in such a way, that one of the 2 lowest notes of the resulting chord matches the root note of the input chord. In addition the method allows to identify input chord""s alternative bass and transpose every note of the subset of the notes to be transposed in such a way, that one of the 2 lowest notes of the resulting chord matches the input chord""s alternative bass. Along with the above-described way the initiation of the input chord can be performed by receiving its root note, chord type and highest note. The task the developers saw for themselves was to create a method of chord transforming, which would let a non-guitar type electronic musical instrument performer emulate the performance of a plucked string instrument with great simplicity and realism, and also let one musician emulate ensemble performance by playing several musical parts simultaneously using the sounds of various instruments with great simplicity and realism, previously assigned different musical instruments"" sounds to different voices of the output chord. As a technical result, achieved in the process of working on the task, there has been developed a possibility for a performer of playing close harmony piano style chords and producing open harmony guitar like multi-voice (up to 6 voices) chords with melodic position (highest note of the chord) on its place. This lets a performer build open harmony multi-voice chord progressions with only one hand, controlling melodic and octave position of every output chord in a natural performing way, i.e. getting the resulting chord""s highest note identical to that of the input chord. This is extremely important for a performer, as the choice of every chord""s melodic position is essential while creating any chord progression, where the upper voice, i.e. melodic line of the highest notes, is the most characteristic and recognizable element of voices leading, bringing all individual chords into a musical form. During the performance of a chord progression as, for instance, a guitar accompaniment to vocal, the choice of chord positions played by the guitarist is extremely important for musical quality of the piece and is carefully thought by the composer or producer, as the melodic line of chords"" highest notes represents important counter point to the lead melody.
Proofs of the realization possibility of chord transforming using the method of the present invention are given below. In particular the method of the present invention can be realized in a described below electronic keyboard musical instrument allowing to emulate guitar and ensemble performance.